Impeller for fluid pump

ABSTRACT

An impeller ( 100 ) for a fluid pump according to the present invention comprises a shroud ( 150 ) that has a disk shape and is drivingly rotated about a center axis, and a cover ( 110 ) comprising a cover main body ( 120 ) having a truncated cone shape with an inlet port ( 123 ) for a fluid formed at a center and a plurality of blades ( 130 ) arranged around a center axis of the cover main body ( 120 ). The cover ( 110 ) and the shroud ( 150 ) are joined to each other with a welding contacting portion ( 135 ) and a welding contacted portion ( 177 ) welded to each other in a center axis direction, in a state where another end surface of the shroud ( 150 ) and a distal end portion ( 131 ) of the blades ( 130 ) are in parallel with each other.

TECHNICAL FIELD

The present invention relates to an impeller used in a fluid pump examples of which including a water pump.

TECHNICAL BACKGROUND

Centrifugal fluid pumps have conventionally been known in which a fluid, sucked in from an inlet port by rotating an impeller with a plurality of blades formed thereon, is pressurized and then is discharged through a discharge port. The impeller includes an open impeller and a closed impeller. The open impeller includes a disk portion provided on only one end portion of the blade, whereas the closed impeller includes the disk portions provided on both end portions to sandwich the blade from both sides (see, for example, Patent Document 1). The closed impeller incorporates a closed space defined by both disk portions to prevent the fluid from flowing out, and thus can be regarded as having a higher pump efficiency than the open impeller.

PRIOR ARTS LIST Patent Document

Patent Document 1: Japanese Laid-Open Patent Publication No. 2011-252481(A)

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The closed impeller has the configuration featuring a shape with both ends of the blades coupled with each other via the disk portions. Thus, when the closed impeller is integrally molded as an injection molded member for example, demolding involves what is known as an undercut portion making the mass production difficult. In view of this, in recent years, it has been a common practice to form an integral closed impeller with one disk portion and the other disk portion, with the plurality of blades formed thereon, separately molded, and then joined together via the plurality of blades. However, this technique has a problem in that an impeller with sufficient joining strength is difficult to form.

The present invention is made in view of the problem described above, and an object of the present invention is to provide an impeller, for a fluid pump, having a simple structure that can achieve high joining strength.

Means to Solve the Problems

To solve the problem described above, an impeller for a fluid pump according to the present invention comprises an impeller main body member that has a disk shape and is drivingly rotated about a center axis; and an impeller cover member comprising: a cover main body having a truncated cone shape with an inlet port for a fluid formed at a center; and a plurality of blades arranged around a center axis of the cover main body. The impeller main body member and the impeller cover member face each other in a center axis direction. The cover main body comprises an inclined portion extending toward the impeller main body member in the center axis direction, while being inclined toward an outer side in a radial direction. The plurality of blades are disposed on a side of the inclined portion facing the impeller main body member. The blades each have a distal end portion, facing the impeller main body member in the center axis direction, provided with a welding contacting portion. The impeller main body member comprises: one end surface facing the impeller cover member; another end surface disposed on an opposite side of the one end surface in the center axis direction; groove portions that are formed at positions matching the blades on the one end surface, and receive the distal end portions of the blades; and a welding contacted portion that is formed in the groove portions and is capable of coming into contact with the welding contacting portion. The impeller main body member and the impeller cover member are joined to each other with the welding contacting portion and the welding contacted portion welded to each other in the center axis direction, in a state where the other end surface of the impeller main body member and the distal end portion of the impeller cover member are in parallel with each other. The entire distal end portions of the blades are not necessarily in parallel with the other end surface of the impeller main body member, and it is sufficient if at least a part of the welding contacting portions of the distal end portions of the blades is in parallel with the other end surface of the impeller main body member.

Preferably, in the impeller for a fluid pump according to the present invention, the blades each comprise: the distal end potion; a first outer surface continuing to a rear side of the distal end portion in a rotation direction; and a second outer surface continuing to a front side of the distal end portion in the rotation direction, the groove portions each comprise: a groove bottom portion that faces the distal end portion in a center axis direction; a first inner surface that continues to a rear side of the groove bottom portion in the rotation direction, and comes into contact with the first outer surface; and a second inner surface that continues to a front side of the groove bottom portion in the rotation direction, and faces the first inner surface, the welding contacting portion is formed in a corner portion between the distal end portion and the second outer surface of the corresponding blade, and the welding contacted portion, as an inclined surface, is formed on the second inner surface of the groove portion. In this case, at least a ridgeline of the corner portion of the welding contacting portion is in parallel with the other end surface of the impeller main body member.

Advantageous Effects of the Invention

In the impeller for a fluid pump according to the present invention, the welding contacting portion of the impeller cover member and the welding contacted portion of the impeller main body member are welded to each other with the distal end portions of the blades of the impeller cover member arranged in parallel with the other end surface of the impeller main body member, and pressure and vibrations applied to the impeller cover member and the impeller main body member with the other end surface side of the impeller main body member serving as the surface to be in contact with an ultrasonic horn. Thus, a lower vibration transmission loss (energy loss in vibration transmission) can be achieved with a pressing surface of the ultrasonic horn being in parallel with a welded portion of the blades and the impeller main body member, whereby stable quality can be achieved with high joining strength. All things considered, the impeller (closed impeller), manufacturing of which including welding for joining between the impeller cover member and the impeller main body member, can achieve higher joining strength to achieve higher pump performance, with a simple structure and with no cost increase. The configuration further has a potential of achieving a complex blade shape and a large capacity pump.

In the impeller for a fluid pump according to the present embodiment, a welded portion between the welding contacting portion and the welding contacted portion is formed as a share joint. The first inner surface serves as a guiding surface when the welding contacting portion is pressed toward the welding contacted portion. The inclined surface of the welding contacted portion might cause the welding contacting portion to move in a separating direction (toward the first inner surface). Still, the first outer surface and the first inner surface are in contact with each other, so that the movement of the welding contacting portion in the separating direction can be restricted. Thus, on the rear side in the rotation direction of the blades, the first outer surface and the first inner surface are in a slidable contact state, whereby a higher positioning accuracy between the welding contacting portion and the welding contacted portion can be achieved at the time of welding. Furthermore, on the front side in the rotation direction of the blades, the welded portion between the welding contacting portion and the welding contacted portion is formed as a share joint, ensuring a large welding area. Thus, even higher joining strength can be achieved between the impeller cover member and the impeller main body member. Furthermore, with this configuration, air is less likely to be mixed at the time of welding, whereby defects such as a void can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view illustrating a water pump including an impeller according to the present embodiment.

FIG. 2 is a cross-sectional view illustrating the water pump.

FIG. 3 is a block diagram illustrating a circulation path of a cooling water that is circulated by the water pump.

FIG. 4 is a perspective view illustrating an impeller according to the present embodiment.

FIG. 5A is a front view illustrating the impeller, and FIG. 5B is a cross-sectional view illustrating the impeller taken along an arrow A-A.

FIG. 6A is a front view illustrating a cover of the impeller, and FIG. 6B is a rear view illustrating the cover.

FIG. 7A is a cross-sectional view illustrating the cover taken along an arrow B-B, and FIG. 7B is a cross-sectional view illustrating a blade of the cover taken along an arrow C-C.

FIG. 8A is a front view illustrating a shroud of the impeller, and FIG. 8B is a front view illustrating a long groove of the shroud.

FIG. 9A is a cross-sectional view of the shroud, and FIG. 9B is a cross-sectional view of the long groove taken along an arrow D-D.

FIG. 10 is a cross-sectional view illustrating a method (welding method) of manufacturing the impeller.

FIG. 11A is a cross sectional view illustrating a state where a welding contacting portion of a blade is in contact with a welding contacted portion of a long groove, and FIG. 11B is a cross-sectional view illustrating a state where a welding contacting portion of a blade and a welding contacted portion of a long groove are welded.

DESCRIPTION OF THE EMBODIMENTS

A preferred embodiment of the present invention is described below with reference to the drawings. A water pump (fluid pump) according to one embodiment of the present invention is disposed in a cooling water circulation path of an engine, and causes forcible circulation of cooling water. First of all, an overall configuration of the water pump is described with reference to FIGS. 1 to 3.

Configuration of Water Pump

A water pump 1 is assembled based on a pump base 10 disposed in a cylinder block of an engine EG. The pump base 10 is provided with an inlet port 11 and discharge ports 12 and 13. The inlet port 11 is connected to a return flow path L2 of the cooling water. The discharge ports 12 and 13 are connected to a discharge flow path L1 of the cooling water leading to a water jacket WJ. The ports 11, 12, and 13 are each open on a front surface side of the pump base 10.

The pump base 10 has a back surface side on which a pump body 20 is detachably attached with a plurality of bolts 21, and thus a pump chamber 2 is formed as a space defined by the pump base 10 and the pump body 20. An O ring 22 is disposed between surfaces of the pump base 10 and the pump body 20 facing each other, to guarantee sealing of the pump chamber 2. The pump base 10 and the pump body 20 form a pump casing.

A pump pulley 40 is attached on an outer circumference side of the pump body 20 via a driving shaft 30. The pump pulley 40 has an outer circumference surface provided with a belt groove 41 by which a drive belt DB, connected to a crank shaft CS of the engine EG, is spanned. The pump pulley 40 is drivingly rotated by receiving rotational force of the crank shaft CS transmitted thereto via the drive belt DB spanned around the belt groove 41.

The driving shaft 30 has a base end portion being press-fitted to the pump body 20, extends through an opening portion 23 of the pump body 20 to the pump chamber 2, and has a rotational axis matching that of the pump pulley 40. The driving shaft 30 is rotatably supported by the pump body 20 via a bearing 31 being fitted to the pump body 20. The driving shaft 30 has a distal end portion to which an impeller 100, disposed in the pump chamber 2, is coaxially attached. The pump pulley 40, the driving shaft 30, and the impeller 100 can integrally and coaxially rotate. A mechanical seal 24 seals between the opening portion 23 of the pump body 20 and the driving shaft 30, to achieve the sealing of the pump chamber 2.

As illustrated in FIG. 3, the pump pulley 40 of the water pump 1 is drivingly rotated by the crank shaft CS of the engine EG, via the drive belt DB. Thus, the driving shaft 30, integrally coupled with the pump pulley 40, rotates together with the impeller 100. The rotation of the impeller 100 causes the cooling water in the return flow path L2 to be sucked into the inlet port 11 and then receive centrifugal force in the pump chamber 2 to be discharged to the discharge flow path L1 through the discharge ports 12 and 13. The cooling water discharged to the discharge flow path L1 is pumped to the water jacket WJ to cool a cylinder and the like of the engine EG, flows to a radiator RD through a connection flow path CL to be radiated, and then returns to the water pump 1 through the return flow path L2 and thus circulates in this manner. The connection flow path CL is provided with a switching valve SV that operates in accordance with a thermostat in such a manner that the cooling water with temperature higher than a predetermined set temperature flows to the radiator RD and the cooling water with temperature lower than the predetermined set temperature flows to a bypath flow path BL. The bypass flow path BL is connected to the return flow path L2, and thus allows the cooling water flowing therein to be directly sucked into the water pump 1 without flowing in the radiator RD. In this manner, the water pump 1 causes the cooling water to forcibly circulate in the water jacket WJ.

Configuration of Impeller

The impeller 100 according to the present embodiment is described by further referring to FIG. 4, FIGS. 5A and 5B, FIGS. 6A and 6B, FIGS. 7A and 7B, FIGS. 8A and 8B and FIGS. 9 and 9B. An upper side and a lower side in an axial direction (center axis direction) are hereinafter also referred to as a “one end side” and a “the other end side”, based on an orientation of the impeller 100 arranged as illustrated in FIG. 5B, for the sake of description. In FIG. 4, FIGS. 5A and 5B, FIGS. 6A and 6B, FIGS. 7A and 7B, FIGS. 8A and 8B and FIGS. 9 and 9B, a hatching of a cross-sectional portion is omitted for the sake of illustration. In each figure, a rotation direction of the impeller 100 is indicated by an arrow

As illustrated in FIG. 4 and FIGS. 5A and 5B, the impeller 100 is what is known as a closed impeller mainly including: a cover 110 on which a plurality of blades 130 are integrally formed; and a shroud 150 joined to the cover 110. The impeller 100 rotates in synchronization with the driving shaft 30 described above, to suck the cooling water through an inlet port 123 formed on the cover 110 and to discharge the cooling water through a discharge port 139 as a space between blades 130.

As illustrated in FIGS. 6A and 6B and FIGS. 7A and 7B, the cover 110 is an integrally molded member made of resin (preferably made of PPS resin), and has a configuration in which the plurality of blades 130 are integrally provided on a cover main body 120.

The cover main body 120 has a truncated cone shape (substantially umbrella shape) with a diameter increasing from the one end side to the other end side. The inlet port 123 having a circular hole shape, through which the cooling water from the inlet port 11 is introduced, is formed through the center of the cover main body 120 in the axial direction. The cover main body 120 has a front surface 121 facing an inner surface of the pump base 10, and has a back surface 122 provided with the plurality of blades (seven blades in the present embodiment) 130 arranged at an equal interval along a circumference direction. The cover main body 120 has a tapered shape (substantially umbrella shape), so that the cooling water can smoothly flow along the back surface 122 of the cover main body 120.

A circumference edge portion 124 of the inlet port 123 in the cover main body 120 is formed to be shorter in the axial direction compared with a conventional configuration as illustrated in FIG. 2. The circumference edge portion 124 has an end surface (left surface in FIG. 2) facing an end surface of a pipe 14 of the inlet port 11 (right surface in FIG. 2) with a slight gap in between. Thus, the closed impeller can be formed with the impeller 100 accommodated in the pump chamber 2 while protruding in the axial direction (left direction in FIG. 2), by a length corresponding to the thickness of the cover main body 120, without increasing the volume of the pump chamber 2, even when an existing pump casing is used. Furthermore, a reverse flow of the cooling water through the gap between the cover main body 120 and the pump base 10 can be reduced.

Each of the blades 130 is formed to have a plate shape curved along a center line including a line curved on one side and a line curved on the opposite side that are continuously connected to each other. The plurality of blades 130 are radially arranged about the axis, with a distance between adjacent blades 130 in the circumference direction gradually increasing from the inner side in a radial direction toward the outer side in the radial direction (that is, in a discharge direction). The blades 130 are each inclined to have a height reducing from the inner side toward the outer side in the radial direction, to conform with the tapered shape of the cover main body 120. Thus, adjacent ones of the blades 130 each have the cross-sectional area set to be substantially the same between an opening on the inner side in the radial direction (suction side) and an opening on the outer side in the radial direction (discharge side), whereby a uniform inner flowrate can be achieved.

The blades 130 each include: a distal end portion 131 facing the shroud 150; a rear side outer surface 132 formed on a rear side in the rotation direction; and a front side outer surface 133 formed on a front side in the rotation direction. The rear side outer surface 132 and the front side outer surface 133 are formed as inclined surfaces and each extend from the one end side toward the other end side in the axial direction while being inclined toward the counterpart by about 2°. Thus, the blade 130 has a shape slightly tapered from the one end side toward the other end side, in a cross-sectional view. The blades 130 are each formed in such a manner that a side on the distal end portion 131 can be received in a corresponding one of long grooves 170 formed on the shroud 150. A corner portion between the distal end portion 131 and the front side outer surface 133 of the blade 130 is formed as a portion (welding contacting portion 135) to be welded with the shroud 150.

As illustrated in FIGS. 8A and 8B and FIGS. 9 and 9B, the shroud 150 includes: a shroud main body 160 formed as an integrally molded member made of resin (preferably, made of PPS resin); and a bush 180 made of metal that is inserted molded in the shroud main body 160.

The shroud main body 160 includes: a boss portion 161 having a cylindrical shape; and a disk portion 165 formed to have substantially the same diameter as the cover 110. The bush 180, having a hollow shape, is buried in the center of the boss portion 161, and is connected to the driving shaft 30 in an integrally rotatable manner. The disk portion 165 has a side of a front surface 166 on which the plurality of blades 130 are welded and thus joined, and has a side of a back surface 167 serving as a surface to be in contact with an ultrasonic horn H at the time of welding (see FIG. 10). Circular balance holes 168 are formed through the front and the back surfaces at three portions of the disk portion 165.

The long grooves 170 are formed at positions matching those of the blades 130, and radially extend from a portion close to the outer circumference surface of the boss portion 161, on the front surface 166 of the disk portion 165. The long grooves 170 each have one end side facing the cover 110 open, and thus can receive the side of the distal end portion 131 of the blade 130.

The long grooves 170 each include: a groove bottom portion 171; a rear side inner surface 172 formed on the rear side in the rotation direction; and a front side inner surface 173 formed on the front side in the rotation direction.

The rear side inner surface 172 is formed as an inclined surface extends from the other end side toward the one end side in the axial direction, while being inclined by about 2° toward a side opposite to the front side inner surface 173.

The front side inner surface 173 includes a first front side inner surface 174, a second front side inner surface 175, and a third front side inner surface 176 that are arranged in this order from a bottom surface side. The first front side inner surface 174 and the rear side inner surface 172 face each other while being separated from each other by a first groove width. The first front side inner surface 174 is formed as an inclined surface that extends from the other end side to the one end side in the axial direction, while being inclined by about 2° toward the side opposite to the rear side inner surface 172. The third front side inner surface 176 and the rear side inner surface 172 face each other while being separated from each other by a second groove width that is larger than the first groove width. The second front side inner surface 175 connects between the first front side inner surface 174 and the third front side inner surface 176 and is formed as an inclined surface that extends from the other end side to the one end side in the axial direction, while being inclined by about 45° toward the side opposite to the rear side inner surface 172. The rear side inner surface 172 serves as a portion that may be in contact with the rear side outer surface 132 of the blade 130. The second front side inner surface 175 serves as a portion (welding contacted portion 177) to be welded with the welding contacting portion 135 of the blade 130.

The excess amount of molten resin produced when the welding contacting portion 135 and the welding contacted portion 177 are welded is stored in a portion, in the long groove 170, close to the groove bottom portion 171 and the third front side inner surface 176. More specifically, a gap between the groove bottom portion 171 of the long groove 170 and the distal end portion 131 of the blade 130, a gap between the third front side inner surface 176 of the long groove 170 and the front side outer surface 133 of the blade 130, and the like function as a resin reservoir for the welding.

In the present embodiment, the distal end portion 131 of the blade 130 and the long groove 170 of the shroud 150 are welded to each other only on the front side in the rotation direction. Alternatively, a method of welding the distal end portion 131 of the blade 130 and the long groove 170 of the shroud 150 to each other on both front and rear sides in the rotation direction may be employed. However, this method involves a risk of producing large residual stress due to the difference in the melting timing between the front and rear sides in the rotation direction. Thus, the welding is preferably performed only on one side (the front side or the rear side) in the rotation direction.

Method of Manufacturing Impeller

Next, a method of manufacturing the impeller 100 according to the present embodiment will be described by further referring to FIG. 10 and FIGS. 11A and 11B. In FIGS. 11A and 11B, the welding contacting portion 135 and the welding contacted portion 177 are illustrated in an upside-down positional relationship to facilitate the understanding of the welding process.

In the present embodiment, the impeller 100 is manufactured by joining the cover 110 and the shroud 150, both made of resin, by ultrasonic welding.

To manufacture the impeller 100 in this manner, first of all, the cover 110 and the shroud 150 are separately molded. The cover 110 is made of synthetic resin and through injection molding using a predetermined mold. Similarly, the shroud 150 is made of synthetic resin and through injection molding using a predetermined mold. In the shroud 150, the bush 180, as a metallic insert member, is formed by insert molding.

Next, the cover 110 and the shroud 150 are mounted to a jig 900. The jig 900 has a substantially cylindrical shape and has an opening portion 901, on an upper side, in which the cover 110 and the shroud 150 can be mounted. The cover 110 and the shroud 150 are mounted in the opening portion 901 of the jig 900 in this order and thus are respectively on a lower side and an upper side. In this process, the cover 110 and the shroud 150 are positioned in the circumference direction, so as to be vertically stacked in the opening portion 901 of the jig 900, with the distal end portions 131 of the blades 130 received in the long grooves 170 of the shroud 150. A guide pin 910, having a shaft shape, vertically stands at the center of the jig 900. The guide pin 910 is inserted through the bush 180 of the shroud 150, and thus the shroud 150 is coaxially arranged with the jig 900. The outermost circumference surfaces of the cover 110 and the shroud 150 and an inner circumference surface of the jig 900 form what is known as a spigot joint structure with which alignment adjustment of the cover 100 and the shroud 150 can be performed. The jig 900 is in surface contact with the side of the front surface 121 (lower side in FIG. 10) of the cover 110. Thus, when the cover 110 and the shroud 150 are mounted to the jig 900, the axis of the cover 110 and the axis of the shroud 150, both extending in the vertical direction, substantially match.

Next, the ultrasonic horn H of a welding machine is brought into contact with the back surface 167 of the shroud 150, and applies ultrasonic vibrations and pressing force to the cover 110 and the shroud 150 vertically stacked, whereby the ultrasonic welding of the cover 110 and the shroud 150 is achieved. More specifically, the pressing force and the ultrasonic vibrations are applied downward, in a state where the sides of the distal end portions 131 of the blades 130 are received in the long grooves 170 of the shroud 150 and the welding contacting portions (corner portions) 135 of the blades 130 are in contact with the welding contacted portions (inclined surfaces) 177 of the long grooves 170.

When the shroud 150 is pressed downward by the ultrasonic horn H, the rear side outer surfaces 132 of the blades 130 come into contact with (and slide on) the rear side inner surfaces 172 of the long grooves 170. Thus, the rear side inner surfaces 172 and the rear side outer surfaces 132 serve as guiding surfaces when the welding contacting portion 135 is pressed toward the welding contacted portion 177. When the welding contacting portion 135 is pressed toward the welding contacted portion 177, an effect of the inclined surface of the welding contacted portion 177 on the welding contacting portion 135 might cause the blade 130 to entirely move toward the rear side inner surface 172 in the long groove 170. Still, the rear side outer surface 132 and the rear side inner surface 172 are in contact with each other, so that the welding contacting portion 135 and the welding contacted portion 177 can stay in contact with each other at an appropriate position. The ultrasonic vibrations produced by the ultrasonic horn H propagate to be concentrated at a contact portion between the welding contacting portion (corner portion) 135 of the blade 130 and the welding contacted portion (inclined surface) 177 of the long groove 170. Thus, frictional heat is generated at the contact portion between the members. Thus, the contact portion melts, whereby the cover 110 and the shroud 150 are welded to each other.

In this manner, a share joint is formed between the welding contacting portion 135 and the welding contacted portion 177, so that a wide welding area can be ensured therebetween, whereby higher joining strength (mechanical strength) can be achieved between the cover 110 and the shroud 150. In the share joint, only the actually melted surfaces of the welding contacting portion 135 and the welding contacted portion 177 are in contact with each other, whereby air is less likely to be mixed at the time of welding. Thus, defects such as a void can be prevented. Furthermore, the joining is achieved with the rear side outer surface 132 and the rear side inner surface 172 in contact with each other. Thus, the rear side inner surface 172 functions as a wall receiving a load acting on the blade 130 while the water pump 1 is in operation.

As described above, in the impeller 100 according to the present embodiment, the welding contacting portion 135 of the cover 110 and the welding contacted portion 177 of the shroud 150 are welded to each other with the distal end portion 131 of the blade 130 (more specifically, a ridgeline of the corner portion of the welding contacting portion 135) arranged in parallel with the back surface of the shroud 150, and pressure and vibrations applied to the cover 110 and the shroud 150 with the back surface side of the shroud 150 serving as the surface to be in contact with the ultrasonic horn H. Thus, a lower vibration transmission loss (energy loss in the vibration transmission) can be achieved with the pressing surface of the ultrasonic horn H being in parallel with the welded portion of the blade 130 and the shroud 150, whereby stable quality can be achieved with high joining strength. All things considered, the impeller (closed impeller) 100, manufacturing of which including welding for joining between the cover 110 and the shroud 150, can achieve higher joining strength to achieve higher pump performance, with a simple structure and with no cost increase. The configuration further has a potential of achieving a complex blade shape and a large capacity pump.

In the impeller 100 according to the present embodiment, the welded portion between the welding contacting portion 135 and the welding contacted portion 177 is formed as a share joint. The rear side inner surface 172 serves as a guiding surface when the welding contacting portion 135 is pressed toward the welding contacted portion 177. The inclined surface of the welding contacted portion 177 might cause the welding contacting portion 135 to move in a separating direction (toward the rear side inner surface 172). Still, the rear side outer surface 132 and the rear side inner surface 172 are in contact with each other, so that the movement of the welding contacting portion 135 in the separating direction can be restricted. Thus, on the rear side in the rotation direction of the blade 130, the rear side outer surface 132 and the rear side inner surface 172 are in a slidable contact state, whereby a higher positioning accuracy between the welding contacting portion 135 and the welding contacted portion 177 can be achieved at the time of welding. Furthermore, on the front side in the rotation direction of the blade 130, the welded portion between the welding contacting portion 135 and the welding contacted portion 177 is formed as a share joint, ensuring a large welding area. Thus, even higher joining strength can be achieved between the cover 110 and the shroud 150. Furthermore, with this configuration, air is less likely to be mixed at the time of welding, whereby the defects such as a void can be prevented.

The present invention is not limited to the embodiment described above and can be refined in various ways without departing from the gist of the present invention.

The embodiment is described above with a share joint as an example. However, the configuration should not be construed in a limiting sense. The embodiment may be applied to an energy direct (ED) joint for example. An example of the ED joint has the following configuration. Specifically, a welding contacting portion, as a triangular protrusion (corner portion) formed on the distal end portion of the blade, and a welding contacted portion, as a flat surface formed in a groove, may be welded to each other. Alternatively, the welding contacting potion as the flat surface formed on the distal end portion of the blade and the welding contacted portion as the triangular protrusion (corner portion) in the groove may be welded to each other.

The embodiment is described above with a water pump driving by an engine as an example. However, this configuration should not be construed in a limiting sense, and the embodiment may be applied to an electric water pump. Furthermore, the present invention is not limited to the water pump, and may be applied to other types of fluid pumps such as a fuel pump and an oil pump.

EXPLANATION OF NUMERALS AND CHARACTERS

1 water pump (fluid pump)

2 pump chamber

10 pump base

20 pump body

100 impeller

110 cover (impeller cover member)

120 cover main body

130 blade

131 distal end portion

132 rear side outer surface (first outer surface)

133 front side outer surface (second outer surface)

135 welding contacting portion

150 shroud (impeller main body member)

170 long groove (groove portion)

172 rear side inner surface (first inner surface)

173 front side inner surface (second inner surface)

177 welding contacted portion

180 bush 

1. An impeller for a fluid pump, the impeller comprising: an impeller main body member that has a disk shape and is drivingly rotated about a center axis; and an impeller cover member comprising: a cover main body having a truncated cone shape with an inlet port for a fluid formed at a center; and a plurality of blades arranged around a center axis of the cover main body, wherein the impeller main body member and the impeller cover member face each other in a center axis direction, the cover main body comprises an inclined portion extending toward the impeller main body member in the center axis direction, while being inclined toward an outer side in a radial direction, the plurality of blades are disposed on a side of the inclined portion facing the impeller main body member, the blades each have a distal end portion, facing the impeller main body member in the center axis direction, provided with a welding contacting portion, the impeller main body member comprises: one end surface facing the impeller cover member; another end surface disposed on an opposite side of the one end surface in the center axis direction; groove portions that are formed at positions matching the blades on the one end surface, and receive the distal end portions of the blades; and a welding contacted portion that is formed in the groove portions and is capable of coming into contact with the welding contacting portion, and the impeller main body member and the impeller cover member are joined to each other with the welding contacting portion and the welding contacted portion welded to each other in the center axis direction, in a state where the other end surface of the impeller main body member and the distal end portion of the impeller cover member are in parallel with each other.
 2. The impeller for a fluid pump according to claim 1, wherein the blades each comprise: the distal end potion; a first outer surface continuing to a rear side of the distal end portion in a rotation direction; and a second outer surface continuing to a front side of the distal end portion in the rotation direction, the groove portions each comprise: a groove bottom portion that faces the distal end portion in a center axis direction; a first inner surface that continues to a rear side of the groove bottom portion in the rotation direction, and comes into contact with the first outer surface; and a second inner surface that continues to a front side of the groove bottom portion in the rotation direction, and faces the first inner surface, the welding contacting portion is formed in a corner portion between the distal end portion and the second outer surface of the corresponding blade, and the welding contacted portion, as an inclined surface, is formed on the second inner surface of the groove portion. 